Silence. “Uh-oh, I think I broke him,” Melora said.

He ignored her. “I just figured out why the young floater colonies spin. It stabilizes them against turbulence. They resist being flipped over.”

“Sorry, not quite,” Melora said. “In their young, fully submerged phase, they can thrive just as well either way up. But you’re on the right track.”

He looked at her. “Please—enlighten me.” He strove to keep the sarcasm out of his voice, for he was genuinely curious.

“The polyps have organs similar to statocysts—a type of balance organ found in many simple invertebrates. Those are sacs with a small amount of inert mass inside, surrounded by sensory hairs. When they move—”

“Its inertia presses it against the hairs on one side, letting the animal sense its direction of motion. Yes, yes.”

She glared at him. “Well, the polyps have something similar, but based on rotation. Instead of an inert mass, it’s a fluid that presses against the side hairs from the centrifugal effect. It gives them a sense of direction and orientation.”

“Then why, pray tell, do they stop spinning when they mature? Have you figured that out yet?”

“Sure. But you’re the engineer, you tell me. Or are you too sick to think straight?”

Aili was looking back and forth between them. “Would you two like to be alone?”

But Ra-Havreii had taken the gauntlet, not wanting Melora to think he couldn’t out-cogitate her on his worst day. “Well, obviously,” he said, masking his embarrassment that he hadn’t seen it right away, “it’s the square-cube law. Only the surface shells contain live polyps, which propel the colony with their tendrils. The surface area, and therefore the number of polyps there are to spin it, rises as the square of its length. But the volume, and therefore the mass they need to propel, goes up as the cube of the length. So it becomes exponentially harder to spin as it grows.”

Melora clapped slowly, sarcastically. “Very good, Doctor. So why does that lead to them rising to the surface once they mature—killing half the colony in the process?”

“Well…” He cleared his throat. “Naturally, they, umm…they need…something that they can only obtain onthe surface. Nutrients to sustain their larger biomass?”

“The juveniles can float to the surface anytime they want, by extracting more oxygen into their flotation bladders. They just don’t have to stay there, since they can expel it again. Why would they choose to throw away the lives of half the colony by staying on the surface permanently?”

“Especially,” Aili put in, “when there’s a risk that a swell could flip them over and kill the other half? Remember, they’re more symmetrical when they’re young.” The mature ones kept growing deeper once they surfaced, naturally becoming asymmetrical since new ones were growing only on the underside. Over time, that lowered their center of mass and gave them greater stability. But Ra-Havreii realized, once Aili pointed it out, that the younger, more symmetrical polyps would be risking the entire colony when they first began their surface existence. What could be worth sacrificing half and risking all for?

“Maybe,” he ventured, “by surfacing and allowing photosynthetic plants to grow on them, they gain access to a new source of nourishment?”

Melora tilted her head approvingly. “Good guess, but you’re overlooking something. The polyps on top still die. The insectoids and animals that inhabit these islets do enough moving around between above and below that the live polyps underneath can collect additional nutrients from their bodies and waste, but the polyps aren’t adapted to survive out of the water. Besides, it takes years, maybe decades for a surface ecosystem to develop enough to provide sufficient nourishment. So what does that leave?”

She was grinning at his inability to solve the riddle, and he racked his brain, desperate to take the wind from her sails. But he just couldn’t see it. Maybe he was just too unwilling to get into the mindset that sacrifice could be acceptable. Yes, there were causes worth fighting for, but the ideal was to win the fight and come out alive. When lives were lost—like the engineers aboard Lunawhen his prototype engine failed catastrophically, like his predeces sor Nidani Ledrah when his design had failed to protect her and Titan’s crew sufficiently from a Reman attack, like so many billions in the Federation when their technology had proven unequal to the Borg—it was a failure, a mistake, a result of inadequate tools or resources. Believing in no-win scenarios was an excuse to avoid admitting inadequacy. And only by admitting your own inadequacy—at least to yourself, no matter how much you denied it to others—could you strive harder to make sure such failures did not happen again.

But of course he was getting off the subject. A colony of floater polyps had no such profound concerns. But the one concern they did have was survival. The goal of life was to stay alive at all costs. If half had to die, there must have been some desperate need, something that would have killed them all otherwise.

“If they get too heavy to swim,” he reasoned, “they would just float in place, or drift randomly. They…they would deplete the resources in their immediate area and be unable to travel elsewhere.”

“Very good,” Melora said, with less snideness this time. “But how does surfacing help them compensate for that?”

Somehow it had to bring them new food sources, but Melora had ruled out all his hypotheses along those lines. He sighed. “Why don’t you just put me out of my misery and tell me already, woman?”

But it was Aili who responded. “Currents,” she said, sounding like it was the most obvious thing in the galaxy. “Once they can’t swim on their own, they need to rely on currents to take them to new nutrient sources—and the surface currents are stronger because of the wind.”

Ra-Havreii supposed he shouldn’t be embarrassed that someone who’d grown up on a pelagic planet would have more knowledge of the subject than he did. But he was nonetheless. It was so obvious. Except…it was nature. How could anyone expect him to know that? If anything, he told himself, he’d been quite brilliant to figure out as much as he had.